Invert Binary Tree

Question

How can I invert a binary tree such that the left and right subtrees of each node are swapped?

Example 1

Input: 
     4
   /   \
  2     7
 / \   / \
1   3 6   9

Output:
     4
   /   \
  7     2
 / \   / \
9   6 3   1

Solution

▭

all//Invert Binary Tree.py

# Definition for a binary tree node.
class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right


class Solution:
    def invertTree(self, root):
        if root == None:
            return None
        else:
            left = self.invertTree(root.left)
            right = self.invertTree(root.right)
            root.left = right
            root.right = left
            return root

▯

all//Invert Binary Tree.py

# Definition for a binary tree node.
class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right


class Solution:
    def invertTree(self, root):
        if root == None:
            return None
        else:
            left = self.invertTree(root.left)
            right = self.invertTree(root.right)
            root.left = right
            root.right = left
            return root